Skymaster 1/6th F-16 speed brake instructions

Preparing for the speed brake installation:

If this is a new installation in an airframe not yet rigged, please skip directly to the installation instruction sequence below.

Before you can install the speed brakes in an airframe that has been rigged, you must first remove the stabs, tailcone, tailpipe and anything that runs inside the rear fuse behind the landing gear bulkhead. Once this is accomplished you will be ready to begin the installation sequence below.

Installation Sequence:

Using a thin line sharpee marker, mark the fuse where the existing fixed speed brake portions will be removed. This is accomplished by using the two templates provided that are marked "hinge covers". Place each template on the top side of the fuse, with the forward edge of each template on the mold seam line just forward of the pivot cover scribes. See Photo below.

The rear edge of each template is where the top of the fuse should be cut on each top and bottom side. Referring to the next photo, mark each line using the sharpee marker and remove the templates. To save a little time, you can mark the pivot cover slot at this time if you wish.

Notice the mark is slightly forward of the original scribe on the fuse. Using a dremel and a diamond cut off wheel (available at Harbor Freight if you don't have one), cut the top side of each speed brake. Be sure and stop right at the top outside edge of the fuse and where shown in the photo.

Notice the outside flat surface will retain the arc present on the speed brake units. Use the operational speed brake units to mark the arc onto each fuse flat side where shown in photo, thus connecting the bottom and top slits.

Flip the fuse over and mark the bottom of each side and repeat the steps above for the bottom cut. See photo below.

Once the slots are cut on both sides of each half, cut the arc and finish using a fine razor saw to complete the cut off sequence. See next photo.

Once each half has been cut off, carefully sand the remaining surfaces with 100 grit paper to remove any rough edges. DO NOT OVER SAND. You only want to straighten up the ragged edges.

The completed halves should appear as below before moving on to the next step.

Use a grinding bit and remove 3/4" of the mold seam glue as shown to the left on the inner and outer edges of the seams. This is necessary for the speed brake glue in plate to fit properly. Also rough sand the entire inner surface of the fuse from 1/2" to 1" inside the rear opening for a good glue surface.

Using the hinge cover templates, mark the location of each hinge cover slot onto the top of each fuse half. See photos below.

Repeat for right side of fuse.

Using the dremel and the diamond cut off wheel, cut out the hinge cover slots as shown in the photo below. Be sure the cut out is no larger than the molded covers. Use the covers as a sizing guide.

Carefully sand the slots until the molded cover fit perfectly within the slots.

Drilling the glue plate tacking holes:

It is necessary to drill a few holes in order to tack the speed brakes in place for alignment prior to epoxying them into the fuse. See photos below.

The left tack hole template shown taped in place (with the fuse upside down). Each side is marked left and right with the top also marked on each template. Once taped in place, drill thru the hole marks shown at the rear of each template using a 3/32-1/8" drill bit. Repeat for each template and fuse half. Each hinge pivot slot template also has one hole located on it. Use this template to drill one hole on the top of the fuse and one on the bottom. For the bottom hole, simply flip the fuse over and place the outer edge of each template (the outer edge is the edge with the shortest distance to a cover slot. There should then be a total of 4 holes drilled on each side of the fuse.

Locate the speed brake mounting spacers (.040X.250X2.5" plastic strips). Tape each speed brake onto the fuse with the spacers mounted where shown in the photo below.

After taping each speed brake in place, use medium CA to tack the speed brake glue plate in place thru the 3/32-1/8" tack holes. Use a bit of kicker to prevent the glue from running. DO NOT ALLOW THE GLUE TO GET ONTO THE HINGE PIVOTS FOR THE SPEED BRAKES. Position the fuse in such a way that when tacking the plates in place, the glue if it were to run, would run away from the pivot plates.

After each side has been tacked in place, carefully remove the tape from each side. Note if the brakes move at all. If they do not, proceed to the next step, if the move, re-tack them once again.

Remove the screws a little at a time, alternating between the top and bottom screws until the clamshells come off.

Once the clamshells have been removed, Aeropoxy the remaining surfaces all around the glue in plate. The only areas not to be glued are along the pivot cover slots. Allow the epoxy to cure for 24 hours before continuing.

Drilling for pushrod cable guide holes:

This section will provide the pushrod guide holes.

Using a 1/4" extension drill bit, drill thru the rear stab bearing bulkhead where shown in photo below and directly thru the stab servo mount bulkhead just forward of the servo mount plate. The hole in the stab servo bulkhead is very close to the bottom of the fuse, so use caution when drilling. The pushrod guide will pass under the stab pivot rod and just under the stab servo on each side of the fuse.

Hole location is approx. 1/4" below and inside the stab bearing bracket's outer lower corner. See inset photo below for further clarification.

Once holes are drilled on each side for the fiberglass guides, assemble the guide/cable/bracket assembly as shown in the photo below.

Assembly the unit as shown above, soldering the two clevis' in place on each end. The cable should extend into each clevis 1/4" after soldering. DO NOT GLUE THE BRACKET AT THIS TIME. Repeat for the second assembly.

With the feet of the brackets facing the front of the fuse, insert the assembly thru the stab servo bulkhead hole and then thru the rear hole in the stab bearing plate. Repeat for the second side. The end of the fiberglass rod is going to stick out beyond the edge of the stab bearing bulkhead 1/16" maximum. See photo below. The cable has been omitted for better clarity of the tube.

Note the fiberglass rod should extend on more than 1/16" past the rear edge of the stab pivot bulkhead.

Servo mount location and gluing:

The servos mount in the rear edge wing recess. See photo below.

The servo mount is shown here mounted along the lip against the rear edge of the wing/fuse blended area. The surface against the right side of the servo mount is the inside of where the leading edge root of the flaperon is located. Rough sand the surfaces and Aeropoxy each servo mount in this location. Allow the Aeropoxy to cure overnight before installing the servos.

You may use a Matchbox or our speed brake electronic system for the next step. Plug in each servo and match the throws. Center the servos with the servo arm (3/4" max arm length) at a 90 degree angle to the long axis of the servo. See photo below.

Notice the servo mounted with the arm facing down when attached. Using a piece of scrap balsa. cut a piece of 1/2sq stock 12-7/8" long and brace it across the inside of the fuse 4" back of the forward edge of the fiberglass cable guide tube. This will position the cable guide in direct line with the servo arm. Rough sand under each guide bracket and Aeropoxy in place. Also apply Aeropoxy to the cable/bracket connection points. The front bracket should be placed 1/2" behind the front edge of the tube and the rear, 4-1/2" behind the front bracket. You may complete both guides at once if criss-cross two sticks before gluing. Allow the Aeropoxy to cure overnight.

Installing the hinge pivot cover plates:

The hinge cover plates are molded plastic with the pivot holes molded in.

The covers attach to the fuse using two different sized piano wires. The larger size wire is for the front pivot and cover stops. The thinner wire is for the closure rods; see template for wire bending template.

Install a 5/8" wide piece of the large diameter piano wire into the front pivot hole of each pivot cover plate. Allow equal parts to extend beyond the outside edges of each cover plate. With the fuse right side up, place each cover plate in place inside the hinge cover slots cut earlier with the pivot wires against the inside surface of the fuse. There should be a 1/64" clearance on the front edge of each cover between the front edge of the cover and the fuse cutout. This is required to allow the cover to open when the brakes extend. After all the covers are taped in place, turn the fuse upside down. Using CA, tack the cover stop wires in place where shown in the photos below. Also tack each front pivot wire in place on both sides of each hinge cover. Repeat for all the cover plates.

Notice the small gap in the front of the installed pivot cover. Also note the stop wire visible thru the slot on the un-installed pivot cover.

Above: One cover has been deliberately left off to show the approx. distance the wire is from the front of the slot. The cover stop wires glue 3/32"-1/8" forward of the rear pushrod holes. This location allows the speed brake pivot arms to clear the stop wires when the brakes are extended. Use Aeropoxy on the ends and middle section of the stop wires and on the ends of the plate pivot wires to make them  permanent. Repeat for second side and allow the epoxy to cure before final installation sequence.

Final Installation Sequences:

In these sections, you will install the clamshells onto the fuse, install the bent pushrod wires for the cover plates and install the clevis' onto the servos for operation.

Carefully remove the tape from the cover plates. Using the wire bending template from the template sheet, bend 4 wires from the thin piano wire stock. The actual sizes may need to be altered to achieve a perfect fit, so do not be discouraged if they aren't on the money with the first try.

With the fuse upside down, hold each clamshell assembly up to the fuse, one at a time. Mark and cut the bottom hinge pivot arms clearance slots into the bottom of each fuse side. The slots are to be 3/16 wide by 3/16-1/4" deep. See photo below.

 Notice the relief slots line up exactly with the pivot arms of the clamshells. Also remove the bottom cover fairing from the clamshells. Replace the removed fairing with the pre-molded fairing that is included with the system. Trim the new fairing as necessary and attach to front side of the fuse side between the speed brake pivot centers using Aeropoxy. The new fairing should hide the hole left when the old fairing part was cut off the rear clamshell. It should also barely touch the inside surface of the clamshell when the brakes are fully closed.  The new fairing will however, be slightly recessed on the front fuse piece. This will not be noticeable after it's painted. The recess can be filled if desired to allow for a smooth contour between the fuse and the added fairing.

Trial fitting the clamshells back onto the fuse halves:

Due to the glue joint around the glue in plate, it mat be necessary to bevel the front upper edge of the pivot assembly to clear the glue fillet on the top side of the glue in plate.

Carefully bevel the top front inside edge of the pivot assembly as necessary for the pivot assembly and clamshells to install onto the fuse with all sides lining up perfectly. Carefully screw the clamshells back onto the fuse. Adjust the bevels as necessary until you get a perfect fit. Once the fit is good, lightly tighten the 4-40 cap screws for each assembly. Double check the gap all around the brake/fuse connection using the spacers that were provided with the speed brake system. Once you are satisfied with the fit, move on to the final assembly/operation sequence.

Attaching the bent pushrod wires to the hinge cover plates:

Locate the very small holes in the top of each brake pivot arm. The holes should be in direct line with the front edge of each brake and approx. 1/4" down from the top of the pivot arm. The long bent side goes into these holes. Insert each bent wire into the hole from the inside of the brake outward so that the bent side of the wire will be on the inside of each pivot arm. Open the speed brake almost all the way, flex the wire as necessary to allow the end of the wire to insert into the rear pivot hole on the hinge cover. Once installed, carefully close the speed brake to check the fit of the cover when the brake is closed. If the cover sticks up when the brake is closed, the wire needs to be shortened slightly, if the wire pulls too hard on the cover when attempting to close the brake, the wire needs to be lengthened. This is necessary due to the very small tolerances in the system. Repeat the above procedure for each cover plate. Once the plates are installed, they require no further adjustment.

Attaching the clevis' for operation:

Turn on your radio and gradually adjust the ATV for each servo so that the clevis will just install onto the servo arm with the speed brakes completely closed. This will be in the direction of the rear of the fuse since the brakes are "Pull open" activation. Be sure the servo will then move in the opposite direction for activation of the brakes once the closed ATV is set. After the clevis' are installed and the closed ATV is set, move the lever or dial on the transmitter to activate the brakes. Adjust the open ATV so that the brakes will open up just short of the stop located on the rear edge of the center activation piston (dead center on the brake assembly). Once the stop is reached, the servo will bind and buzz. Back off from that setting just 2-3% on the ATV. Max open is 60 degrees for flight, but only 42 degrees for landing. If you can place the brakes on a 3 position switch, this is easily achieved. Pos #1, closed, pos#2, 42 degrees, pos#3 full open 60 degrees. Be sure to use servo slow in the open direction and normal speed for closed. The brakes will operate the most realistically this way.

Painting and final finish:

You may paint the fiberglass parts of the inner brake unit and the plastic parts that do not move, but, DO NOT PAINT ANY OF THE PIVOT ASSEMBLY or PISTON ASSEMBLY as the units ultra smooth function is a direct result of very tight tolerances that would be ruined by paint getting into any of the tight surface areas. Be careful when spraying the outsides as well and overspray can also ruin the units smooth function. The best way is to paint the parts with a brush and then apply a slight weathering with a very thin weathering wash and an airbrush on very low pressure. The insides of all F-16's speed brakes are white regardless of station and get very dirty. The only exception are the Thunderbirds. Bright, clean white would be the color then. Only then would a very small amount of weathering be necessary.

If you have any problems installing your speed brake system, give us a call or e-mail us.

M-F 9-6 MST USA.  208-233-4721 or e-mail   support@details4scale.com